The invention relates to electronic payment mechanisms in telecommunications networks and particularly to an electronic payment system comprising first processing means for generating electronic receipts corresponding to received payments, second processing means for receiving said receipts, and transfer means for transferring said receipts between the first and second processing means.
As the use of telecommunications networks has increased, the use of electronic payment mechanisms has become more common. In the near future, payments for different services, physical goods or information will be more and more often transferred between buyers and sellers in the form of electronic money. These are generally called electronic tokens.
The introduction of electronic payment systems has been delayed by uncertainty with respect to security. At the protocol level, development of standards has advanced considerably, and e.g. the SET standard (Secure Electronic Transaction), which will be introduced soon, comprises several encryption and authentication functions, by means of which data transmission related to transactions can be implemented reliably.
At the application level above the protocol level, practice and practical applications still vary greatly. Accordingly, several countries have drawn up rules and regulations to protect consumers against errors and abuse in connection with electronic transactions. For example, the United States has issued Regulation E stipulating that systems intended for carrying out electronic transactions must provide receipt of all transactions executed by the system and at regular intervals provide a written specification of transactions for the subscriber. This has been typically implemented in such a manner that after each transaction the system sends a record functioning as an electronic receipt to the unit that stores the subscriber""s electronic tokens.
Such a receipt is fully sufficient for an ordinary subscriber who uses the electronic payment system for simple personal payments. There are, however, a large number of users whose payment transactions are more complicated, and therefore smooth registration, transfer and authentication of receipts is more important. For example, an employee, who can afterwards charge certain expenses from his employer, or a consult, who has several, projects at the same time and charges each project separately for his expenses, either has to acquire separate units (hereafter referred to as purses) for storing electronic tokens for each invoicing destination or is forced to waste time on storing, verifying, converting and transferring receipts for invoicing purposes at different destinations. The former way quickly becomes difficult to manage as the number of purses increases. The latter is time-consuming and does not allow the user to utilize benefits provided by advanced data transmission.
On the other hand, the end-receiver of the receipt, e.g. an employer, customer or tax authorities receiving tax-deductible bills, needs to be sure that the receipt is related to a real transaction and originates from the payee. It is difficult to acquire separate certified receipts, and in the case of small telephone bills this is even unprofitable. Certification based on a bank statement in turn weakens the invoicing person""s information security, since in that case the person who receives the specification also receives information on all transactions related to the subscriber""s purse.
An object of the invention is to develop an electronic payment system, in which transactions involve a certified, undeniable electronic receipt, which can be easily transferred and by means of which the payer""s information security can be protected with respect to other payments when the receipt is transferred. An electronic receipt substantially comprises information units represented by means of electric or magnetic charge levels, and these units can be read and written by means of electronic equipment.
The object of the invention is achieved with the electronic payment system described in the introduction, characterized in that first processing means are arranged to encrypt the electronic receipt to be generated or part of it, if necessary, with a public-key algorithm by using the payee""s own secret key as an encryption key; and second processing means are arranged to decrypt a received receipt with a public-key algorithm by using the payee""s public key as a decryption key.
The invention also relates to a method as claimed in claim 13 for acknowledging a transaction in the electronic payment system, which comprises first processing means for providing electronic receipts corresponding to payments, second processing means for receiving said receipts, and transfer means for transferring said receipts between the first and second processing means. The method is characterized in that said electronic receipts or parts of them are encrypted with a public-key algorithm by using the payee""s private key as an encryption key; and receipts are decrypted with a public-key algorithm by using the payee""s public key as a decryption key.
The invention is based on the system comprising means for encrypting an electronic receipt either completely or partially with a digital public-key algorithm. Encryption is carried out by using the payee""s private key, whereby the encryption functions as an electronic signature in the receipt. If the recipient of the receipt wants to be convinced of the authenticity of the receipt, he decrypts the encryption with the payee""s public key. The receipt is in electronic form, and thus it can be easily read and transferred between different destinations. Digital encryption with the payee""s private key certifies the origin of the receipt undeniably. As long as the receipt is in encrypted form, it cannot be read if the payee is not known exactly, and counterfeiting of information included in the encrypted parts of the receipt is impossible.
The part of the receipt to be encrypted preferably comprises a transaction identifier, on the basis of which the seller can identify the transaction in his own transaction register, the sum paid and a description of the subject of payment. The encrypted text also preferably comprises a check field, by means of which it can be verified that the decryption has been correctly performed. Encryption can also be optional, whereby it is used only when the receipt is needed in certified form.
An advantage of the method and system of the invention is that users of the electronic payment system can provide undeniably certified receipts of transactions and transfer them to further processing, with maintaining the level of certification. Payments that are to be transferred to different destinations for storing or crediting can be paid from the same electronic purse regardless of the final payer, without having to compromise information security of the purse in connection with crediting of payments.